Radio broadcast distributing system



March 19, 1929.

E E. CLEMENT Original Filed May 23.,v 1925 RADIO BROADCAST DISTRIBTING SYSTEM 2 Sheets-Sheet 1 Moat/Iron March 19, 1929. E. g. CLEMENT I l706,383

I RADIO BROADCAST DISTRIBUTING SYSTEM Original Filed May 21, 1925 2 Sheets-Sheet. 2

Patented Mar. 19, 1929.

UNITED STATES PATENT OFFICE.

EDWARD E. CLEMENT, OF WASHINGTON, DISTRICT OF COLUMBIA, ASSIGNOR TO EI)- WARD F. COLLADAY, OF WASHINGTON, DISTRICT OF COLUMBIA.

RADIO BROADCAST DISTRIBUTING- SYSTEM.

Original application iiled May 21, 1925, Serial No.y 31,928. Divided and this application led June 25,

1926. Serial No. 118,488.

My invention relates to systems of radio broadcast distribution and more particularly to a relaying system for organized distribution. The present applicatlon is a division of my copending application Serial No. 31,928, filed May 21, 1925.

Very briefly stated, this system includes subdivision of the ultimate units or subscribers stations into local groups in local areas, each group related to a local or regional distributing station; the grouping of these regional stations according to districts and the relation of the district stations to a central master station. There may be more intermediate steps or stations interposed between the subscribers control or regional station and the central master station and there may be direct connection between the said regional stations and the central master station, but these possible variations will be apparent from the detailed description and do not change the principle involved. In any case, for pur poses of distribution, the central master station broadcasts to the district master stations on divisional carrier wave frequencies, each of the district master stations broadcasts to its constituent regional central stations on a fixed carrier wave frequency, and each local or regional central station broadcasts to the subscribers in its local area on a common fixed carrier wave frequency.

Thus it will be apparent that the first characteristic feature of the system is that of sending from each center to the class or order of centers next above or below it, on a fixed carrier wave frequency or frequencies allotted permanently to said next higher or lower order of stations. If we call the central master station of the entire system, A, and call the district master stations B, the local or regional distributing stations C; and the subscribers instruments in general D, then we may say that A transmits to B on B frequency, B transmits to C on C frequency, and C transmits to D pn D frequency, of the respective carrier waves. For information that goes through from A to D, or that goes through from B to D, as well as information originating with C, original modulations are actually repro'- Renewed March 8, 1927.

duced in the instruments at D, by means which will be described. The simplest wa to do this is by double modulation, which7 also enables easy change of carrier wave frequency at the intermediate or relaying stations.

My invention is illustrated in the accompanying drawings, in which:

Fig. 1 shows symbolically an arrangement of double modulating and transmitting equipment at the A or master station of the system for matter originating there.

Fig. 2 shows symbolically equipment for the B stations, by means of which the primary carrier waves transmitted from the apparatus of Fig. l may be demodulated and the intermediate frequency waves or envelope modulated upon a new carrier wave C.

Fig. 3 shows symbolically apparatus similar to that in Fig. 2, but intended to be located at the local or regional distributing stations C, receiving, therefore, on the C Wave frequency, and transmitting on the D or subscribers frequency.

Fig. 4 shows symbolically a` subscribers set adapted to receive on the D frequency, to demodulate the short carrier wave, and then to demodulate the intermediate frequency carrier wave, so as to produce audio waves as its output.

Fig. 5 is a similar circuit diagram of the apparatus shown in Figs. 2 and 3, which is the same in construction and arrangement, but differently tuned according to the station B or C, at which it is located.

Fig. 6 is a circuit diagram of a subscribers receiving set arranged for selection through double modulation.

Referring now to Figs. 1 to 4 inclusive, and first to Fig. 1, I have shown therein an arrangement for originating broadcast transmission at the head or master station A. The purpose is double modulation, by first modulating by means of a telephone transmitter upon a long wave, and then modulating the long wave upon a short carrier wave of suitable frequency to be received at the stations B. It goes without saying, that this same arran ement of apparatus will be found at eaclgl of the other central stations B and C. In order that this apapratus may also be employed for radio broadcasting of material brought into the stations over wired trunks, I show a jack J1o connected through an amplifier to switch contacts which may be connected through switch arms to the primary of the transmitter induction coil, 302, the secondary of which is connected to the modulator of the generating and transmitting set. Thus a trunk line or even a subscribers Wire may be plugged on to the modulator through the amplifier by means of jack J 1.

Fig. 2 shows a relay apparatus primarily intended for use at stations B and C, but which Will also be used at master station A. Fig. 3 shows identical apparatus, except for the jacks 303 and 304, the purpose of which will be presently explained. These jacks can be used in the circuit of Fig. 3 if desired.

The function of the apparatus of Fig. 2 is to take double modulated Waves at the frequency allotted to the receiving station, demodulate the short Wave carrie',` so as to produce modulated intermediate frequency waves which are then passed through a tuned amplifier 305 to a modulator 30G, by means of which they are modulated on a primary or short Wave carrier of a frequency suitable for the next lower order of receiving stations, in this case C stations. The short Waves thus modulated are then radiated.

By means of the jack 303, intermediate frequency or long Waves modulated may be taken off a trunk and passed through the amplifier 305 to the modulator 30G and thence radiated as before. Also, by means of the jack 304 intermediate frequency or long Waves modulated which have passed through the dernodulator 307 and the amplifier 305 may be forthwith placed upon the Wire trunk lines for transmission to other stations. These extensions should be available at each stage in the system, and I consider it original With me to provide means for affecting these combinations of superaudio frequency modulated Waves transmitted either from wires to radio carrier or from radio carrier to Wires Without change either in the intermediate frequency Waves or in their modulations, and shall claim the same accordingly. This is one essential feature of the present system, which it is believed should be adhered to in any system of organized broadcasting, i. e. that when an original modulation is once made, the Wave train carrying that modulation should be preserved unchanged throughout its entire course from point of origin to the listeners ears.

Referring to Fig. 4, this shows typically a subscribers 'apparatus for taking double modulated Waves sent out from the stations of any of the preceding three figures, and

demodulating the same so as to recover the original audio modulations make them apparent. There are two units, one a demodulator of the short carrier Wave, which produces the long intermediate frequency Wave carrying the original audio modulations, and passes these to the second demodulator, which demodulates the intermediate waves and passes the audio waves to the telephone receiver shown at the right of the figure. This method if shown in detail in my copending application referred to above, where the circuit arrangement of such a double demodulator is illustrated in full.

The apparatus shown in Figs. 2 and 3, is intended to receive a double modulated carrier Wave such as that radiated from the antenna in Fig. 1, demodulate the same and reiinpose the long Wave or intermediate frequency, with its modulations, upon another short Wave carrier which in the apparatus of Fig. 2 is supposed to be the carrier Wave of the frequency allocated to stations C, While in the apparatus of Fig. 3 this is supposed to be the carrier Wave of a frequency allocated to the subscribers stations D. Glancing at the four figures, 1, 2, 3 and 4, it will be observed that from the original modulation due to the transmitter to the final demodulation by the intermediate wave demulator in Fig. 4, the same intermediate long wave carrier, and the same audio modulations thereof, are maintained intact and unmodified, being merely passed along by relaying from station to station on short carrier waves, or an equivalent of the carrier Waves F-wTM/Mwo" i`i'w-i" mi um The apparatus in Fig. 2 and that in Fig. 3 is identical except for the tuning of the transmitted carrier Wave. The description of one therefore will suffice for both.

Referring to Fig. 5, Which is a detailed circuit applicable to both these figures, 54 is the receiving antenna coupled at 174 to the grid circuit of the detector 170, Whose plate circuit is connected through a tuned filter coupler 175 to the grid circuit of the amplifier tube 171, whose )late circuit is connected through the transtlormer 176 to the grid circuit of the modulator tube 172, which in turn has the usual I-Ieising connections 178-179 to the circuit of the oscillator tube 173; the radio choke coil l178, the power battery B14 and the magnetic choke coil 177, being arranged as usual. The grid and plate of the oscillator' tube 173 are connected to the antenna inductance coil 180, which with the usual tuning condenser 180a is included in the antenna circuit 55. Filament batteries B11, B13, and B15, and plate batteries B12 and B16 are located as usual. As thus described, the assemblage constitutes a relay set which will take in the modulated long Waves on a short Wave carrier, and retransmit them on a carrier of different frequency,

without demodulating o1' disturbing the modulations of the intermediate or long wave. In order that these long waves may be transferred from the first detector circuit to trunks and in order that modulated long waves brought in by trunks may be placed on the radiating antenna 55, I provide connections symbolized as jacks .IQ-J9". The jack J 9 has its springs connected to thc terminals of the coupler 17 5, and these springs normally rest upon contacts in the plate circuit of the tube 170. The jack J9 has its springs connected to the terminals of the coupler 176, and these springs normally rest on contact-s connected in the grid circuit of the modulator tube 172. Trunks such as 50 and 51 terminate on jacks J6 and J 7 and are adapted to be interconnected with each other or with the jacks J 9 and J 9 by plugs and cords as indicated at P5 and P". By pluging either one of the trunk jacks J 6 or J 7 onto jack J 9, the corresponding-1I trunk line will be connected to the tuned filter coupler 175, whose windings are simultaneously disconnected from the detector tube 170. Thus modulated carrier current at the same frequency as the intermediate waves used in the radio side of the system, will come over the trunk line 50, for example, through the jacks J 6 and J9 and plugs P5 and P, and so to the coil 175, whence the long waves will pass to the grid circuit of the amplifier tube 171, to be amplified and then sent through the modulator and oscillator circuits of tubes 172 and 173. Any incoming trunk material can in this way be put on the air at any station having the relay apparatus of Fig. 8 or the equivalent thereof. For reverse operation, by plugging either one of the trunk jacks J or J7 on to the jack J 9, the corresponding trunk, as 57 for example, becomes connected through plug PG and plug P5 to plug J 9 and therethrough to the coil 176, Whose primary winding is simultaneously disconnected from the grid circuit of the modulator tube 172. The incoming modulated short carrier waves received on the antenna 54 will pass through the detector 170 and demodulation of the primary carrier long intermediate frequency Waves will be passed through the filter coupler 175, amplified by the tube 171, and so communicated through the coupler 176 to the cord circuit and jacks, directly to the trunk line 51. In this way, material can be taken off the air at any time and put on the trunks by simply obliterating the primary carrier Wave. It it to be understood that by varying the tuning of the couplers, long Waves of any frequency can be taken from or fed onto the trunks. Thus, the mechanism shown in Fig. 5 contains within itself all the elements necessary for transfer from the receiving antenna to a trunk or trunks, of

modulated super-audio carrier current; for transfer of modulated superaudio carrier current or Waves from a trunk or trunks by modulation on to a short carrier wave, to the antenna 55 for radiation; and for transfer from trunk to trunk between the stations of audio or superaudio modulated waves or carrier current. It will be understood of course that the mechanism and circuits described are typical only, and in this specific form are used for purposes of definition and not of limitation. I consider the arrangement and combinations shown in Fig. 5 to be new and original with me and shall claim the same accordingly.

A simple form of circuit arrangement for the subscriber-s receiving set symbolized in Fig. 4 is that shown in Fig. 6. This comprises a. receiving antenna 28 coupled to the input circuit of a detector tube 30 tuned to the primary wave and a second detector tube 31 having its input circuit coupled through a filter coupler 33 to the output or plate circuit of the first detector 30, the filter coupler 33 being t-uned to the intermediate frequency. The second detector 31 of the subscribers set has its output circuit coupled through an audio transformer 34 to the input circuit of an amplifier tube 32 whose output circuit is cou led through a transformer 35 to a loud spea er 36. T e usual A and B batteries are provided as indicated at A1 and B1, respectively, the A battery lead 25 being connected to the filament bus 43 through a filament switch h.

What I claim is:

1. In an organized system of radio broadcast distribution, means for transmitting a short primary carrier wave modulated wlth a relatively long intermediate frequency carrier wave and this modulated in turn with an audio signal, and means for relaying the same comprising a primary demodulator and a modulator transmitter, for transferring the modulated intermediate frequency or long carrier wave without change in its characteristics or modulations to a different short carrier wave, together with a Wire circuit tuned to said intermediate frequency extending between stations and connecting the primary demodulator at one station With the modulator transmitter at another' station.

2. In an organized system of radio broadcast distribution, a relay transmitter for double modulated waves comprising a demodulator, an amplifier, a modulator and an oscillator transmitter in combination therewith, together with means for connecting a wire circuit between the receiving demodulator and the amplifier so as to cut off the demodulator and connect with the input circuit of said amplifier or between said amplifier and the transmitting modularadio carrier wave to radio carrier Wave, but from radio carrier Wave to Wires and vice versa.

In testimony whereof I hereunto alix my signature.

EDWARD E. CLEMENT.

118,488, Clement 4 references cited f3192511222221+f ,Mgg uolpitts 1,452, 957 250-15 Espensched 1,597,993 do Shreeve 1, 378,982 Z50-15x British 142,371 250-15 Morecroft PP680,683 1921 Edition, Clement 1,695,180 25015 fr J o 

